1. Field of the Invention
The present invention relates to a flip-cover opening/closing device for a foldable electronic apparatus, and more particularly, to a hinge mechanism for a flip-cover of a portable cellular phone which enables one to detach the flip-cover from the phone body upon rotating the flip-cover over a communication angle and applying a force.
2. Description of the Related Art
In a portable cellular phone, since dial button keys and function button keys are disposed on a surface of a body thereof, the buttons can be inadvertently pressed when the phone is carried by a user. To prevent such a malfunction, a button cover, or a flip-cover, is frequently provided to protect the phone body. As the length of the cellular phone is shortened, the transmitting sensitivity is lowered due to loss of transmitted sound volume during calling. Such problems can be overcome by using the button cover to reflect the transmitted sound and thereby improve the quality of the transmission.
In a conventional portable cellular phone having a button cover, two hinge pins and a coil spring positioned therebetween are disposed in a cylindrical hinge arm. The hinge pins, which are made of plastic, have cam surfaces on their outer ends. Metal cam followers are fitted to either side of the phone body do as to respectively contact the cam surfaces of the two hinge pins. The cam surfaces have indented portions and protrusions which interact with the cam followers so that the hinge mechanism either keeps the button cover closed or allows the button cover to remain in a stable and open position at a predetermine angle with respect to the phone body. I have noticed however, that when a user repeatedly opens and shuts the button cover, the cam surfaces of the hinge pins wear out due to the friction between the plastic surfaces of the hinge pins and the metal surfaces of the cam followers. I have also found that when a user applies an excessive force to the button cover, the cover may be detached from the body and the hinge assembly elements are often expelled and lost due to the force of the coil spring. Furthermore, cracks may occur in either the hinge assembly or in the body of the phone due to the excessive force applied to the cover.
Takagi, et al., U.S. Pat. No. 5,111,503, endeavors to provide a Portable Telephone Set with one cover in an effort to eliminate many of the problems noted above. The hinge of Takagi et al is somewhat cumbersome to manufacture and assemble, and due to its dependence upon a set of U-shaped springs, is not especially reliable for long term use.
Subsequently, Takagi, et al. U.S. Pat. No. 5,303,291 designed a PORTABLE TELEPHONE HAVING A DETACHABLE FUNCTIONAL MODULE and Kobayashi, U.S. Pat. No. 5,317,785 designed a HINGE MECHANISM FOR FOLDABLE ELECTRONIC APPARATUS; both designs use hinge mechanisms that are not particularly amenable to either disassembly or replacement of broken or worn parts. Moreover, if the distal ends of the cover serving as hinges become cracked, the entire cover as well as its internal microphone, must be removed and discarded, and a new complete cover installed.